The invention relates to a novel method and apparatus for enviromental protection and gas cleaning and in one case to flue gas cleaning for reducing particulate emission incident to the combustion of biomass material.
The number of large cogeneration plants burning wood chips and other biomass materials is on the increase. One of the biggest problems these plants face is meeting the air pollution requirements. The present invention could solve this problem.
One application for the invention is to reduce the particulate emissions from the flue gas of biomass cogeneration facilities. Cogeneration plants are able to generate electricity for their own use and sell the excess to an electric power company. Such plants also use the generated steam for processing. Almost any biomass material can be burned for fuel. Examples are wood chips, nut hulls or the like.
The prior art includes the Dauvergne U.S Pat. No. 4,098,200 which shows combustion gases passing over the incoming fuel. Recirculation systems in the prior art include Maitilasso U.S. Pat. No. 3,515,078; Gibeault U.S. Pat. No. 3,815,523; and Paul U.S. Pat. No. 4,089,277.
The present methods of cleaning flue gas include baghouses, precipitation, washing and scrubbing. Both the operating costs and the capital expense related to such methods are extremely high. In addition, they have a relatively short operating life. These high costs and short operating times tend to discourage strict compliance with environmental laws.
An oject of this invention is to provide a simple, inexpensive, effective and practical means of cleaning gases and particularly the dirty flue gas from biomass combustion systems such as steam boiler systems.
An additional object of the invention is to utilize the energy of a hot flue gas to increase the overall efficiency of the system.